In an interview with 60 Minutes, she couldn't contain her excitement and almost started the conversation with the words: "Can I just say I'm pregnant?"

She and her fiancé said: "We're having a baby."

"We're stoked we couldn't be happier ," Hoskin said.

"Turia told me she's the happiest she's ever been."

Turia Pitt and her partner Michael Hoskin the day after competing in the Ironman World Championships in Hawaii. Picture: Michael Klein

Pitt, 29, found out she was pregnant just three days before she was about to take part in a Mount Everest trek.

She was set to lead the trek from May 10 to May 28 with Interplast, which provides life-changing surgery and medical training in across the Asia-Pacific.

While the trek went ahead, she pulled out of it, saying it was too risky for her to do.

"I wanted to do the walk .. it's not just myself I have to think about now," she said.

She said her first reaction when she did her first pregnancy test which came back positive was: "Like f**k".

"Ok stay calm, go fold your clothes and put them away."

Inspiration speaker and athlete Turia Pitt.Contributed

Her fiance, Hoskin, was brushing his teeth at the time and she left the pregnancy stick there for him to see.

He said he had a mouthful of toothpaste at the time.

Pitt, who is 15 weeks pregnant, is expected to carry her first child without any issues as she suffered no internal injuries when 65 per cent of her body was burned when she was trapped by a bushfire during the Kimberley ultra marathon in 2011.

The couple said they were amazed when they saw the first ultrasound of their baby.

"When we saw ours we thought oh my god look at its arms and legs," she said.

Pitt said she thought Hoskin was going to be an "amazing dad".

"Michael's going to be an amazing dad he was so patient so caring (with me)," she said.

"I think those qualities in a parent are really desirable."

Pitt added that it makes her happy she is still alive today.

"It makes me stoked I'm still here. Not every woman in the world gets to experience this and I get to with my best friend, my partner," she said.